From 5751215ffa8f48a2b109c10f6c6a4dcb9debc3e2 Mon Sep 17 00:00:00 2001
From: dogeystamp <dogeystamp@disroot.org>
Date: Sat, 26 Oct 2024 18:25:07 -0400
Subject: [PATCH] feat: uci engine interface

---
 Cargo.toml        |   2 +
 src/bin/engine.rs | 133 ++++++++++++++++++++++++++++++++++++++++++++++
 src/movegen.rs    |   2 +-
 3 files changed, 136 insertions(+), 1 deletion(-)
 create mode 100644 src/bin/engine.rs

diff --git a/Cargo.toml b/Cargo.toml
index 723e31f..954df3b 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -4,6 +4,8 @@ version = "0.1.0"
 edition = "2021"
 license = "GPL-3.0-or-later"
 
+default-run = "engine"
+
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]
diff --git a/src/bin/engine.rs b/src/bin/engine.rs
new file mode 100644
index 0000000..189b764
--- /dev/null
+++ b/src/bin/engine.rs
@@ -0,0 +1,133 @@
+/*
+
+This file is part of chess_inator.
+
+chess_inator is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 3 of the License, or (at your option) any later version.
+
+chess_inator is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License along with chess_inator. If not, see https://www.gnu.org/licenses/.
+
+Copyright © 2024 dogeystamp <dogeystamp@disroot.org>
+*/
+
+//! Main UCI engine binary.
+
+use chess_inator::fen::FromFen;
+use chess_inator::movegen::{FromUCIAlgebraic, Move, MoveGen, MoveGenType, ToUCIAlgebraic};
+use chess_inator::Board;
+use std::io;
+
+/// UCI protocol says to ignore any unknown words.
+///
+/// This macro exists to avoid copy-pasting this explanation everywhere.
+macro_rules! ignore {
+    () => {
+        continue
+    };
+}
+
+/// UCI engine metadata query.
+fn cmd_uci() -> String {
+    let str = "id name chess_inator\n\
+                id author dogeystamp\n\
+                uciok";
+    str.into()
+}
+
+/// Parse the `moves` after setting an initial position.
+fn cmd_position_moves(mut tokens: std::str::SplitWhitespace<'_>, mut board: Board) -> Board {
+    while let Some(token) = tokens.next() {
+        match token {
+            "moves" => {
+                for mv in tokens.by_ref() {
+                    let mv = Move::from_uci_algebraic(mv).unwrap();
+                    let _ = mv.make(&mut board);
+                }
+            }
+            _ => ignore!(),
+        }
+    }
+
+    board
+}
+
+/// Sets the position.
+fn cmd_position(mut tokens: std::str::SplitWhitespace<'_>) -> Board {
+    while let Some(token) = tokens.next() {
+        match token {
+            "fen" => {
+                let mut fen = String::with_capacity(64);
+                // fen is 6 whitespace-delimited fields
+                for i in 0..6 {
+                    fen.push_str(tokens.next().expect("FEN missing fields"));
+                    if i < 5 {
+                        fen.push(' ')
+                    }
+                }
+
+                let board = Board::from_fen(&fen)
+                    .unwrap_or_else(|e| panic!("failed to parse fen '{fen}': {e:?}"));
+                let board = cmd_position_moves(tokens, board);
+
+                return board;
+            }
+            "startpos" => {
+                let board = Board::starting_pos();
+                let board = cmd_position_moves(tokens, board);
+
+                return board;
+            }
+            _ => ignore!(),
+        }
+    }
+
+    panic!("position command was empty")
+}
+
+/// Play the game.
+fn cmd_go(mut _tokens: std::str::SplitWhitespace<'_>, board: &mut Board) {
+    let mvs: Vec<_> = board.gen_moves(MoveGenType::Legal).into_iter().collect();
+    let chosen = mvs.first();
+    match chosen {
+        Some(mv) => println!("bestmove {}", mv.to_uci_algebraic()),
+        None => println!("bestmove 0000"),
+    }
+}
+
+fn main() {
+    let stdin = io::stdin();
+
+    let mut board = Board::starting_pos();
+
+    loop {
+        let mut line = String::new();
+        stdin.read_line(&mut line).unwrap();
+        let mut tokens = line.split_whitespace();
+        while let Some(token) = tokens.next() {
+            match token {
+                "uci" => {
+                    println!("{}", cmd_uci());
+                }
+                "isready" => {
+                    println!("readyok");
+                }
+                "ucinewgame" => {
+                    board = Board::starting_pos();
+                }
+                "quit" => {
+                    return;
+                }
+                "position" => {
+                    board = cmd_position(tokens);
+                }
+                "go" => {
+                    cmd_go(tokens, &mut board);
+                }
+                _ => ignore!(),
+            }
+
+            break;
+        }
+    }
+}
diff --git a/src/movegen.rs b/src/movegen.rs
index 8ccc042..5cc22d2 100644
--- a/src/movegen.rs
+++ b/src/movegen.rs
@@ -168,7 +168,7 @@ pub struct Move {
 
 impl Move {
     /// Apply move to a position.
-    fn make(self, pos: &mut Board) -> AntiMove {
+    pub fn make(self, pos: &mut Board) -> AntiMove {
         let mut anti_move = AntiMove {
             dest: self.dest,
             src: self.src,